1. Field of the Invention
The present invention involves methods of deterring illicit copying of electronically published documents by creating unique identification codes specific to each subscriber. Each copy of the published document has a unique arrangement of electronically created material, e.g. print material or display material, which is not quickly discernable to the untrained human eye and not destroyed by distortion or noise of a copying machine. These unique identification codes discourage illicit copying and enable a publisher/copyright owner to analyze illicit copies to determine the source subscriber.
2. Detailed Background
When the quality of reproductions from copy machines became comparable with the original, the cost of copies was reduced to a few pennies per page, and the time it took to copy a page was reduced to a second or less, then copy machines started to present a threat to publishers.
The problem of identifying illicit copies is intensified due to minute distortion and noise inherent in physical copying. These distortions are normally greater in the horizontal direction when the document is reproduced on a copy machine. Conversely, when a facsimile machine is used, the distortion is more predominate in the vertical direction. Preventing an individual from duplicating a document that is in his possession is an extremely difficult, if not impossible task. Instead of trying to prevent duplication of documents, the present invention is directed to making electronic publishing more acceptable by making it possible to identify the original owner of a bitmap version of the text portion of a document. The present invention should be adequate to discourage much of the copying and distribution that might otherwise occur. A result of the present invention method is that a publisher or copyright owner can more readily determine who the original belonged to when reproduced copies are found.